1. Field of the Invention
The present invention relates to an imaging device, an imaging method and a computer readable storage medium, particularly to an imaging device and an imaging method with a white balance control function which realizes a good white balance correction.
2. Description of the Related Art
There has been a widely used technique in the field of an imaging device to determine a light source of uniform light in an entire captured image and perform the same level of a white balance correction on the entire image. However, a problem may arise in this technique when a captured image is illuminated with different kinds of light sources that the same level white balance correction is not suitable for such an image.
In view of solving such a problem, Japanese Laid-open Patent Publication No. 2002-271638 discloses a white balance control to prevent color shifts in the entire image by dividing a captured image into small areas and performing white balance correction on each of the small areas, for example. Also, Japanese Laid-open Patent Publication No. 2005-347811 discloses a more advanced white balance control to perform white balance correction on each pixel in order to resolve color shifts in a boundary of the small areas, for example. Moreover, Japanese Laid-open Patent Publication No. 2007-129622 discloses a white balance control function to divide a color image into small areas in association with types of light sources based on brightness of illumination and calculate a correction coefficient for each of the divided areas.
However, the techniques disclosed in the three documents have a problem that when a subject is illuminated with a plurality of light sources, different levels of white balance are done on the single subject, which causes generation of an unnatural image. Another problem is that, depending on a captured scene, the area division of an image based only on brightness components is not good enough for proper white balance correction in association with types of light source. This is because a yellow color shows a relatively high brightness while a blue color shows a low brightness and a blue color in a sunny area may show lower brightness than a yellow color in a shadow area.